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Until the publication of MEG4, the content on this site is intended to raise awareness of the enhancements coming. OCIMF will not be clarifying content further until the publication of MEG4 to avoid any confusion between the current MEG3 and forthcoming MEG4

What’s Coming in MEG4

Meg 4 Cover

The Mooring Equipment Guidelines has been fully reviewed and updated for the fourth edition.

New chapters and key changes include:

  • Enhanced guidance for the purchasing, condition monitoring, and retirement of mooring lines and tails.
  • Enhanced guidance on documentation of mooring equipment.
  • New chapter on the Human Factors in Mooring Design.
  • New chapter on Jetty Design and Fittings.
  • New chapter on Ship Shore Interface.
  • New chapter on Alternative Technologies.

The updated guidance addresses the questions raised by reader since the third edition was published in 2005. We have reviewed not only the technical content, but also the language so that the information provided is clear and easy to understand.

The guidance within MEG is sure to enhance the safety of mooring from the design of mooring arrangements using a Human Centred Design approach and an increased focus on the use and understanding of mooring lines and tails.

Video Coming soon


New Terminology

During the revision of MEG it was clear there is confusion in the shipping industry with the term Minimum Breaking Load (MBL) and other terminology relating to line strength.

Further, there was no industry guidance on condition-based monitoring of mooring lines and tails.  Since nearly all mooring injuries are a result of mooring line failures, OCIMF has strived to provide guidance and clarity on the condition-monitoring of mooring lines.  Below is a list of some new terms that will be introduced in MEG 4.  We also encourage you to visit the Clarifications section HERE for further information.

Ship Design Minimum Breaking Load

The minimum breaking load of new, dry mooring lines for which a ship’s mooring system is designed, to meet OCIMF standard environmental criteria restraint requirements. The ship design MBL is the core parameter against which all the other components of a ship’s mooring system are sized and designed with defined tolerances.

Nylon (polyamide) mooring lines should be specified as break tested wet because nylon lines change strength characteristics once exposed to water and generally do not fully dry to their original construction state.

Line Design Break Force - LDBF

LDBF is the minimum force that a new, dry, spliced mooring line will break at when tested according to appendix B. This is for all mooring line and tail materials except those manufactured from nylon which is tested wet and spliced. This value is declared by the manufacturer on each line’s mooring line certificate (see appendix B) and is stated on a manufacturer’s line data sheet. As outlined in appendix B, when selecting lines, the LDBF of a line shall be 100%–105% of the ship design MBL.

The LDBF for nylon (polyamide) mooring lines should be specified as break tested wet because nylon lines change strength characteristics once exposed to water and generally do not fully dry to their original construction state.

Working Load Limit - WLL

The maximum load that a mooring line should be subjected to in operational service, calculated from the standard environmental criteria. The WLL is expressed as a percentage of ship design MBL and should be used as a limiting value in both ship design and operational mooring analyses. During operation, the WLL should not be exceeded.

In the same way that SWL is a limit for fixed equipment, the WLL value is used as a limit with the standard environmental criteria and mooring layout when designing mooring systems in establishing mooring system designs. Steel wire ropes have a WLL of 55% of the ship design MBL and all other cordage (synthetic) have a WLL of 50% of the ship design MBL.

Line Management Plan - LMP

LMP is used to manage the operation and retirement of mooring lines and tails. The LMP also documents the requirements, assumptions and evaluation methods used in determining the line retirement criteria. The LMP is specific to an operator, ship type, and trade route; however, MEG4 gives general guidance on establishing a LMP.

Mooring System Management Plan – MSMP

The MSMP which will complement the ship’s safety management system. Through a ‘goal-based’ approach core elements of the mooring system are identified, against which high level ‘goals’ are established supported by more detailed ‘functional requirements’. A register of the mooring system components is maintained for the ship’s life in an accompanying Mooring System Management Plan Register (MSMPR).


Summary

The updated MEG4 represents the output of a multi-discipline working group representing members of various shipping trade organisations, mooring line manufacturers, equipment suppliers, shipyards, and OCIMF members.

The OCIMF Secretariat and Working Group participants are currently working through the document to address editorial comments received through the publication management process. These updates include revisions to text, illustrations, and photographs to ensure a technically accurate document that is easy to read.

Meg4 Coming Soon

Expected Release Date: Second Quarter 2018

Related Links

Clarifications

Below are a list of Clarifications that have been received during the review process of MEG 4 and through technical queries received by the secretariat. Clarifications will be periodically amended or added based on technical queries received.

MBL will be replaced with the following new terms: Ship design MBL, Line Design Break Force (LDBF), and Working Load Limit (WLL).

Historically, the multiple definitions, test and calculation methods for mooring line break force ("MBL") have led to confusion between users and manufacturers and often a discrepancy between expected and actual mooring line performance (e.g. nominally similar mooring lines may in the past, have had a variation in tested break force of +/-10%). To resolve this confusion, OCIMF has collaborated closely with Eurocord, Cordage Institute, shipping industry NGOs, and OCIMF members to clearly define a set of terms and test methods for mooring line “MBL” that can be used consistently by both line users and manufacturers when designing, specifying, testing and operating mooring lines.

Traditionally, due to the use of the term ‘Minimum’ Breaking Load, many mooring line users may have evolved the misunderstanding that lines can be safely loaded up to their MBL with no failures or degradation. This is not the case and OCIMF is trying to heighten the understanding of the importance of safety margins on mooring lines.

MBL will be replaced with the following new terms: Ship Design MBL (MBLSD), Line Design Break Force (LDBF), and Working Load Limit (WLL).

OCIMF is striving to enhance mooring safety for the industry and provide clarification. These new terms will align the cordage and the tanker industries to a common language.

Further, OCIMF is striving to address the issues and frequent confusion that have risen within the industry when Ship owners incorrectly believe that mooring line certificates must match exactly the MBL requested.

Use of the term “LDBF” improves clarity from previous terminology where the term “MBL” was used in different contexts. Using LDBF makes it clear that the rated force stated is a function of the design of the mooring line.

Use of the term LDBF helps to bring a clear and common language on rope terminologies between the Ship operators and the cordage industries. E.g. the cordage industry uses cordage institute references such as CI-1500. ISO standards refer to a MBL with un-spliced ropes; however, the CI-1500 spec refers to a spliced rope. These differences can lead to an LDBF and MBL differences greater than 10%. Further, while the term MBL is commonly referred to across the cordage industry, manufacturers may still utilize different forms of statistical analysis in the process of deriving their specifications.

Ship Design Minimum Breaking Load – The minimum breaking load of new, dry mooring lines for which a ship’s mooring system is designed, to meet OCIMF standard environmental criteria restraint requirements. The ship design MBL is the core parameter against which all the other components of a ship’s mooring system are sized and designed with defined tolerances.

Nylon (polyamide) mooring lines should be specified as break tested wet because nylon lines change strength characteristics once exposed to water and generally do not fully dry to their original construction state.

LDBF is the minimum force that a new, dry, spliced mooring line will break at when tested according to appendix B. This is for all mooring line and tail materials except those manufactured from nylon which is tested wet and spliced. This value is declared by the manufacturer on each line’s mooring line certificate (see appendix B) and is stated on a manufacturer’s line data sheet. As outlined in appendix B, when selecting lines, the LDBF of a line shall be 100%–105% of the ship design MBL.

The LDBF for nylon (polyamide) mooring lines should be specified as break tested wet because nylon lines change strength characteristics once exposed to water and generally do not fully dry to their original construction state.

WLL The maximum load that a mooring line should be subjected to in operational service, calculated from the standard environmental criteria. The WLL is expressed as a percentage of ship design MBL and should be used as a limiting value in both ship design and operational mooring analyses.During operation, the WLL should not be exceeded.

In the same way that SWL is a limit for fixed equipment, the WLL value is used as a limit with the standard environmental criteria and mooring layout when designing mooring systems in establishing mooring system designs. Steel wire ropes have a WLL of 55% of the ship design MBL and all other cordage (synthetic) have a WLL of 50% of the ship design MBL.

Although technically more accurate to relate the WLL to the specific mooring LDBF, the differences between ship design MBL and LDBF of varying manufacturers will be negligible and using the ship design MBL allows for a single value for analysis and comparison.

Ship design MBL is the stated value around which a ship’s mooring system is designed and established at the ship design stage. Mooring lines are selected with a LDBF value equal to or within 100-105% of the ship design MBL. To allow line manufacturers to offer mooring lines without manufacturing a bespoke line for each ship design MBL requested.

Not necessarily; MEG4 has left the specification of QA testing (e.g. review of LDBF, Linear Density, Tenacity, etc) to the discretion of the user. However, recommendations on quality assurance testing are provided within MEG4.

The margin between WLL and ship design MBL is necessary to account for the following:

  • The unknowns and variability of real life ship-shore mooring operations, when compared with theoretical calculated mooring analysis
  • Even when a mooring line is new, the actual force necessary to cause a mooring line to fail in operation may be lower than the LDBF due to environmental conditions (e.g. temperature or swell periods) and mooring arrangements (eg. D/d)
  • The actual force necessary to cause a mooring line to fail will decrease the more the mooring line is used.

Not necessarily. OCIMF recognises that in some circumstances it may be necessary or unavoidable to exceed the WLL of the mooring line. The mooring line user will develop procedures for managing the risk posed by lines that have exceeded the WLL as part of their Line Management Plan.

The LMP is used to manage the operation and retirement of mooring lines and tails. The LMP also documents the requirements, assumptions and evaluation methods used in determining the line retirement criteria. The LMP is specific to an operator, Ship type, and trade route; however, MEG4 gives general guidance on establishing a LMP.

Typical components include: records of mooring hours, line inspection records & plans, manufacturer & operator retirement criteria, test/inspection reports and manufacturer recommendations following tests or inspections.

It is recommended.  The ship operator is responsible for the development and implementation of the ship’s LMP. The LMP contains the ship operator’s requirements for the management of mooring line maintenance, inspection and retirement during the operational phase of the mooring line lifecycle.

The LMP can be a standalone tool or it may be integrated into existing safety or maintenance management systems. It can be available as hard or electronic copy, or both. Whatever the format, the LMP should be capable of being updated. It should be accessible for internal and external compliance verification, ship personnel training and communication with manufacturers. LMP information should be stored in a location that is easy for all users to access, e.g. on a computer system that can be accessed from both the ship and shore or compiled in a single physical location. It should be easy for the system users to access the LMP information from a single physical or virtual location.

In the development of the new mooring line guidance in MEG4, OCIMF has recognised that break force (“MBL”) is just one of a wide range of performance and operating parameters that can influence mooring line performance. Performance Indicators provide information, in a standardised format, on the relative influence of each parameter (e.g. D/d, temperature) This allows candidate mooring line designs to be compared during the procurement process and an assessment of the relative influence of operating parameters to be made whilst the lines are in service.

No. The mooring line manufacturer undertakes all testing related to Performance Indicators as part of the MEG4 guidance on purchasing and testing of mooring lines and tails. The results of these tests are entered into the Line/Tail Base Design Compliance Certificate and are repeated in summary on the Mooring Line/Tail Certificate for each line.

MEG4 has a dedicated appendix explaining the testing and documentation steps necessary for manufacturers to demonstrate they have followed the OCIMF guidelines.  When all necessary steps have been completed, the manufacturer enters the information into a Line/Tail Base Design Compliance Certificate which is then reviewed and endorsed by an “Independent Inspector” (typically from a classification society). A completed and endorsed certificate should always be requested as part of the line procurement process and OCIMF will encourage manufacturers to make their certificates publicly available (e.g. on manufacturer web-sites).

The brake rendering should always be set to 60% of the ship design MBL. This is because the brake render setting point is the main protection for a Ship’s mooring system, and protects all parts of the mooring system by rendering at a specific pre-determined setting which is below all other failure loads but above line WLLs. The mooring winch brake becomes a weak link within the mooring system.

It is important that brake rendering value is above the WLL of the line. When operational mooring analyses are carried out they verify that the Ship can remain safely moored for the given OCIMF Standard Environmental Criteria, within the given limits for heave surge and sway, without exceeding the maximum values for any of the mooring system components (shore hooks, lines, fittings and winches.) Thus brake rendering values need to be higher than WLL values in order that the mooring studies can provide appropriate verification. If brakes rendered at WLL, software simulations would generate Ship movements that would exceed limits. i.e. It is important that there is a margin between brake rendering set point and the maximum loads to which lines should be exposed in maximum anticipated environmental conditions. Again, the mooring winch brake becomes a weak link within the mooring system.

Mooring line MBL is no longer a recognised term in MEG4. However OCIMF appreciates that it will take time for the terminology to be adopted throughout the industry. In such cases it depends on the reason that the terminal is asking for the line strength information. If this is not known, the Ship should either provide the terminal with both ship design MBL and LDBF values referencing alignment to MEG4, or request further clarification from the terminal. If the terminal needs the information for operational mooring analysis, then the LDBF values for each line should be provided.

Yes. In MEG4 all mooring tails are designed to be over strengthened by 125-130% of ship design MBL. Therefore the mooring tails are subject to the same 100 to +105% tolerance in LDBF as the mooring lines. In MEG4, there is an increased focus on mooring tail construction and design and application to ensure they follow the same principles and testing requirements as mooring lines.

Over strength of mooring tails is to account for the increased mechanical wear and tear that mooring tails typically experience (when compared to mooring lines) from jetty hooks and bollards and deployment/retrieval. In addition tails experience higher rates of loss because they are made from fibres that are less resilient against tension fatigue and provide a higher amount of elastic energy absorption. While they also get handled abused during handling, the work they perform accelerates their fatigue rate.

Ships built to MEG4 will already have a ship design MBL to satisfy OCIMF Standard Environmental Criteria restraint requirements and each mooring line will have a LDBF. Mooring fittings and mooring winch brake rendering values are based on the ship design MBL.

Ships built prior to MEG4 should still follow the same guidance of setting their mooring winch brake rendering values based on the “line MBL” which, should be assumed to be synonymous with the ship design MBL, which is termed “Design Rope” MBL (See Figure 7,3 in MEG3).

Design Stage: At the design stage a mooring analysis tool should be utilised to determine what restraint forces are required for the Ship. This output is the ship design MBL.

Operational Stage: For mooring analysis performed during the operational stage of a Ship and terminal, the LDBF should be used, in order to model actual conditions as realistically as possible. However, WLL values (limits) should be based on ship design MBL.

MEG is based on OCIMF Standard Environmental Criteria. If your vessel was based on IACS environmental criteria you should seek guidance from IACS.